How to Fix Outlook PST File does not shrink when using Compact Now (2023)

Sometimes your Outlook Data File (.PST) can become so large that even if you delete emails and then manually click “Compact Now” the file does not shrink.

This can leave you with a PST file that just gets larger and larger, taking up more of your hard drive space.

At this point, the best method is to export the emails you want to save to a new PST file. This PST file will not contain any of the deleted emails and so is much smaller. You can them make this PST file your primary data file, and delete your old bloated PST file.


How to Shrink your Outlook Data File (PST)

  1. Go to “File” -> “Open & Export” -> “Import/Export”
    Outlook Import Export
  2.  Select “Export to a File”.
    Outlook Export to a file
  3. Next select file type “Outlook Data File (.pst).  
    Outlook Export to a data file
  4. Select the Outlook Folder(s) to export from. If you want to include subfolders, make sure to tick “Include Subfolders”
    Outlook Export Data File Mailbox Selection
  5. Now save the exported file – I have chosen “MyNewCompactedMailbox.pst” but you can choose anything. You can put the new data file in the same directory as the old file – this will make it easier to transfer over as you can just rename the old file to “Outlook_OLD.pst” and rename the new file to the same as what the old file was. To make sure nothing is deleted, tick “Allow Duplicate items to be created”.
    Outlook Export to new data file
  6. Click “Finish”. You will be asked to set a password. Just leave this blank and click OK.
  7. Close the Outlook.
  8. Go the directory where the old PST and your new PST are saved. It will most likely be something like C:\Users\yourname\Documents\Outlook Files\
  9. Rename Outlook.pst as “Outlook_OLD.pst”
  10. Rename “MyNewCompactedMailbox.pst” as Outlook.pst.
  11. Open Outlook. You can use your new (smaller) mailbox immediately. However, you will not be able to receive emails correctly until you choose a new delivery location for each email account.
  12. Go to “File” -> “Account Settings” -> “Account Settings”
  13. Click on the email account you want to fix, and then click “Change Folder”
    Outlook Account Settings Change Data file
  14. Choose your new Outlook Data File, and then select the inbox.
    Outlook New Email Delivery Location

Repeat steps 13 and 14 for each email account.

Once you have tested your new (smaller!) mailbox and have made sure that everything works, you can delete your old PST file.

Hopefully this has fixed your issue with Outlook. We have an article which covers another Outlook bug: What is Token Factory iFrame on Mac? which you may also find useful.